A semi connected operation is known as a function implemented on an upper layer of CDMA2000 series advanced by use of technologies such as an OFDM (Orthogonal Frequency Division Multiple Access) and the likes.
In the semi connected operation, for the purpose of power saving, a semi connected state is provided in which, although a MAC-ID (Media Access Control Identifier) is assigned, a reverse link (RL) is not transmitting, while an assigned part of a forward link (FL) continues receiving. Since it is possible to transit from the semi connected state to an open state by providing the semi connected state, it achieves faster transition than transition from an idle state to the open state.
The semi connected state is adopted by CDMA2000 Air Interface Evolution (Loosely Backwards Compatible: LBC) (see Non-Patent Document 1) and effective when used at reception of PPT (Push To Talk). For example, two or more terminals (Access Terminal: AT) are dealt as a group for PTT in a cellular system (Push To Talk On Cellular: PoC) and are placed in a standby state (idle state) or a reception state simultaneously.
More specifically, two or more terminals are grouped and, when one terminal in the group is calling, other terminals are set in the reception state, so as to be used for a purpose of dispatch operation group call or the likes. In this operation style, the terminals are only receiving most of the time. That is, minimization of transmission on the reverse link contributes to a reduction in power consumption. Such scheme for reducing power consumption of a terminal is disclosed in “WIRELESS COMMUNICATION SYSTEM” (Patent Document 1), for example.
Incidentally, transition from a standby state to a call state takes time as it requires to path through an access state and obtain MAC-ID. Since paging is monitored at paging monitor intervals (normally set at between 1 to 10 seconds), it delays start of a call. Therefore, it is not possible to avoid breaking up of a beginning part of the call.
On the other hand, the semi connected state enables reception of a common channel on the forward link from the base station at any time. That is, information on assignment of the forward link sent in each frame (normally, 5 to 500 ms) is continuously monitored. In the semi connected state where a terminal can return to the open state quickly and “there is less breaking up of the beginning part of the call”, the terminal does not consume a resource of a traffic channel while holding MAC-ID assigned thereto.
In the semi connected state, the access terminal operates as follows:
(1) In a power saving state
(2) No transmission on the reverse link (transmission of a reverse control channel)
(3) Holding MAC-ID
(4) Periodically monitoring assignment information of the reverse link or the forward link (F-SCCH: Forward Shared Control Channel)
The semi connected state is canceled by access (Access Attempt) for transmission on the reverse link, that is, when the terminal transits into the open state.    Patent Document 1: Japanese Patent Application Laid-Open No. 2004-172772    Non-Patent Document 1: 3GPP2 TSG-CC21-20061030-009R2-Qualcomm_Semi Connected_Mode.pdf